The search company has rewritten its market leading Yahoo! Mail service entirely in HTML5, optimizing it specifically for iPad. The new interface looks superb and provides easy access to a number of features normally found in Apple’s built-in Mail client and rival Gmail web app (which is also optimized for the iPad).

The speedy and responsive web app uses local data caching, providing access to the previously retrieved messages when offline. You can also view photo attachments in-line or preview them separately. Yahoo went to great lengths to optimize the graphics, layout, and user interface to mimic the appearance of Apple’s native Mail app down to a two-pane layout in landscape. In fact, the only thing giving it away is the address bar in Safari. Yahoo’s product manager Lee Parry wrote the following in a blog post:

If you’ve used our recently launched HTML5 mobile Web mail for iPhone you’ll feel right at home. We’ve kept all the things users love about our new mobile Web mail experience, while also optimizing for the gorgeous large screen of the iPad.

Other features include full message search, smart folders that automatically collect messages based on a custom criteria, and searching across folders. The new web interface can be accessed via Safari on iPad at http://mail.yahoo.com.